False twist texturizing method and apparatus

ABSTRACT

Yarn is false twisted first in one sense and then in the opposite sense to produce an essentially zero torque texturized yarn. For this purpose, false twist spindles are provided to twist the yarn in opposite senses.

[151 3,656,288 451 Apr. 18, 1972 United States Patent Gilchrist [56] Reierences Cited UNITED STATES PATENTS [54] FALSE TWIST TEXTURIZING METHOD AND APPARATUS Mattingly...

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Primary Examiner-Stanley N. Gilreath Assistant Examiner-Werner H. Schroeder Attorney-Nolte and Nolte Related US Application Data [63] Continuation-impart of Ser. No. 789,653, Dec. 26,

1968, abandoned, which is a continuation of Ser. No. 661,319, Aug. 17, 1967, abandoned.

ABSTRACT Yarn is false twisted first in one sense and then in the opposite [30] Foreign Application Priority Data sense to produce an essentially zerotorque' texturized yarn.

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17 Claims, 7 Drawing Figures PATENTEDAPR 18 I972 SHEET 3 OF 4 BY 74w 7% ATTORNEYS PATENTEUAPR 18 1912 sum 0F 4 mNx INVENTOR flag/N440 52-25 Y); c/w/sr Zara xWLm ATTORNEYS ing yarn on the run and is particularly, although not exclusively, applicable to thermoplastic yarn.

. :It is well known to crimp yam such as continuous filament polyarnide or polyester yarn by passing the yarn over a heater and then through a false twist device which imparts a twist in the yarn as it travels over the heater, whereby the yarn is set in its twisted configuration, and then untwists the yarn as it leaves the device.

Yarn crimped in this manner has superior bulkiness, and handling and knitting properties compared to uncrimped yarn. Such yarn, however, has the disadvantage that it tends to be of high stretch, and that it tends to snarl easily. It also has the disadvantage that it has high torque so that it tends, when knitted, to produce a fabric of high spirality by which is meant that a tube, for example, of fabric knitted on a circular knitting machine will have successive courses displaced circumferentially from one another, so that the tube as a whole will be twisted spirally overall.

Attempts have been made to overcome these disadvantages by various forms of heat treatment of the yarn subsequent to thefalse twist crimping. However, it has been found that such post heat treatment often has the effect of considerably reducing the bulk of the crimped yarn produced, and in some cases does not sufiiciently reduce the torque in the yarn to enable fabric of satisfactorily low spirality to be produced therefrom. It is an object of the present invention to provide methods and apparatuses for producing false twist crimped yarn in which at least some of the above disadvantageous characteristics are eliminated or reduced;

1 According to one aspect of the invention, a method of crimping yarn on the run includes false twisting the yarn a first time on one direction and heating the yarn while twisted, and then false twisting the yarn a second time in the opposite direction without heating the yarn between the first and second false twisting steps.

According to the invention, it is found surprisingly that by subjecting the yarn to a false twist crimping operation and then subjecting the yarn to an opposite false twist operation without further heating, it is possible to produce a yarn which is bulky, has low stretch, and knits into fabric having little or no spirality.

lt is believed that this is because the yarn, contrary to prior belief on the matter, is in a' condition immediately after the conventional false twisting operation to be still readily susceptible to further permanent distortion by mechanical forces without application of a heat setting step. This may be because there is sufficient internal heat retained in the yarn to enable these further distortions to be heat set without the addition of further heat if immediately inserted, particularly when these further distortions are effected by twisting.

According to another aspect of the present invention a method of crimping yarn on the run includes heating the yarn, subjecting the yarn to a'first false twisting operation in one direction so that the yarn is heated in its first twisted configuration, and then subjecting the yarn to a second false twisting operation in the opposite direction without further heating,

' the yarn being oppositely twisted by the second false twisting operation while it possesses sufiicient heat to be at least partly permanently deformable.

According to yet another aspect of the present invention, a method of crimping yam on the run includes heating and false twisting the yarn a first time in one direction so that the yarn is in a twisted configuration when being heated, immediately false twisting the yarn a second time in the opposite direction so that the yarn is twisted in the opposite direction by the second false twisting simultaneously with being detwisted from the twist in said one direction imparted by the first false twisting.

It is believed that twisting the yarn in one direction by one false twisting operation and then immediately twisting the yarn in the opposite direction by a second false twisting operation as the first twist is removed is an important physical factor in the production of yarn having the desirable characteristics mentioned above, in that it causes the yarn to be twisted directly from a twist in one direction to a twist in the opposite direction, this violent reverse twist: treatment of the yarn assisting the permanent deformation of the twisting operation.

The yarn may be subjected to a temperature of from about 150 to about 250 C. when being heated.

The twists imparted by the two false twisting operations may yarn by the second be equal in magnitude, and each may be within the range of 50 to turns per inch. However, the number of twists imparted by the second falsetwisting operation may be less or greater than the number of twists imparted by the first, depending upon the characteristics required in the crimped yarn.

Optionally, the yarn may be provided with additional heat during the second, i.e., reverse, false twisting operation to augment the heat retained by the yarn from the prior heating.

According to a further aspect of the present invention, apparatus for crimping yarn comprises a first false twist device arranged to rotate the yarn in one: direction, a heater so disposed as to heat the yarn as it travels to the first false twist device, a second false twist device arranged to rotate the yarn in the opposite direction, and guide means for guiding the yarn without further heating from the first false twist device to the second false twist device.

The first and second false twist devices may be separate false twist heads. 7

Alternatively, the two false twisting devices may comprise one false twist having two twist tubes.

According to a still further aspect of the present invention apparatus for carrying out a method as described above comprises a first twist stopper, a heater, a first false twist device for twisting the yarn in one direction and causing this twist to run back past the heater to the first twist. stopper, a second false twist device for twisting the yarn in the opposite direction on leaving the first false twist device, and a second twist stopper for stopping the running back of the twist inserted by the second false twist device, characterized in that the second twist stopper is formed by the first false twist device.

'In another aspect of the invention, each of the false twisting operations is carried out by frictionally engaging the running yarn with at least one surface moving in a direction having a component transverse to the direction of movement of the yarn.

The invention also provides an apparatus for crimping yarn comprising a false twist device having an endless movable track provided with a surface for frictionally engaging the yarn, means for advancing yarn under tension from a supply of yarn, guide means for guiding the yarn so that it crosses said surface substantially transversely to the direction of movement of the surface first in one direction and then in the opposite direction whereby a first twist can be imparted to the yarn in one direction and a second twist can be imparted to the yarn in the opposite direction, and a heater for heating the yarn passing in said one direction to the surface of the endless track.

There may be provided a further movable endless track having a surface for frictionally engaging the yarn and cooperating with the first such endless track, the yarn path being adjustable and the further track being movable so that the surface thereon moves transversely to the path of movement of the yarn in a direction for twisting the yarn in the same direction as the first twist or in the same direction as the second twist.

The endless track or tracks may comprise an annular member or members the inner surface or surfaces of which are adapted for engaging the yarn.

in the case where two annular members are provided the members may be mounted for rotation about parallel axes spaced so that the openings in the members are out of register with one another.

In'one embodiment of the invention, the annular members may be mounted for relative movement towards and away from one another whereby their respective openings can be brought into and out of register with one another.

In any of the arrangements referred to above in which said endless tracks are formed by annular members, the annular members may be mounted at adjacent ends of two hollow cylindrical members mounted for rotation about spaced parallel axes and axially displaced with respect to one another and, the remote ends of said cylinders may have additional annular members mounted therein having inner surfaces for engaging the yarn.

The inner surfaces of the annular members may be convexly curved to provide smoothly curved paths for said yarn passing over said inner surfaces.

In any of the arrangements referred to above, there may be provided a twist stopper for engaging the yarn prior to the heater.

According to another aspect of the invention, an apparatus for crimping yarn comprises a false twist device having at least two endless movable tracks formed with surfaces for frictionally engaging the yarn, means for advancing yarn under tension along a path which successively crosses said surfaces transversely to their respective directions of movement and which tracks are movable so that in use their respective surfaces impart twist in opposite directions to the yarn, there being a twist stopper for engaging the yarn before it engages the first of said surfaces and a heater for heating the yarn between the twist stopper and the first of the surfaces.

In some instances, between the heater and the first false twisting, there may be provided means to impede cooling of the yarn over this part of the yarn path.

In order that the invention may be more readily understood, embodiments thereof will now be described by way of example with reference to the accompanying Figures, in which:

FIG. 1 is a perspective view of one embodiment of apparatus for crimping yarn according to the invention;

FIG. 2 is a front elevation of part of a second embodiment of apparatus for crimping yarn according to the invention;

FIG. 3 is a perspective view of another apparatus for crimping yarn according to the invention;

FIG. 4 is a part elevation, part sectional view of the apparatus shown in FIG. 3;

FIG. 5 is an end view of the apparatus shown in FIG. 4;

FIG. 6 is an end view of a swingable part of the apparatus shown in FIG. 5, shown in a different attitude; and

, FIG. 7 is a sectional view of a locking mechanism for the swingable part of the apparatus.

Referring to FIG. 1, it will be seen that yarn 10 is supplied from a package 11 and passes via a wire finger tensioner 12, ceramic guide 13 and an adjustable magnetically restrained tensioning and twist stopping pulley 14 of a known kind to ceramic guides 15 at the lower end of a heater 17. The pulley 14, in addition to preventing twist in the yarn running back to the supply package 1 1, also serves to control the tension in the yarn during its upward passage over a heating surface 16 of the heater 17.

The heater 17 is heated by means of electrical resistance wires (not shown) and its heating surface 16 is provided with grooves (not shown) within which the yarn passing over the heater is guided.

After passing over the heating surface 16, the yarn passes through a twist tube 40 of a false twist head 18 of the kind disclosed in U.S. Pat. No. 3,355,870, in which the tube 40 is held in contact with a driving pulley by means of a permanent magnet. The head 18 is driven by means of a continuous belt, part of which is shown at 19, engaging a driving spindle 41 of the head 18. The belt 19 is driven in a known manner by means of an electric motor (not shown). The tube 40 is provided at its yarn exit end in a known manner with a diametrical twisting bail (not shown) around which the yarn is wrapped.

The yarn is passed from the tube 40 around a guide 20 and then through a twist tube 42 of a false twist head 21 which is of the same kind as head 18. The head 21 is driven by the belt 19 two heads to impart unequal false twist to the yarn. Altema-- via a driving spindle 43 so as to rotate the tube 42 in the same direction as the tube 40, but it is to be noted that because the yarn travels through the tube 42 in the direction opposite to its direction of travel through the tube 40, the two heads apply false twist in opposite directions to the yarn travelling through them.

We have found that we obtain good crimping results in practice if the heads 18 and 21 and twist tubes 40 and 42 are identical so that the false twist imparted by each is equal;

However, it is possible, if desired, by using driving spindles or driving pulleys or twist tubes of different diameters for the tively, the heads can be driven by separate bolts travelling at different speeds to provide unequal false twisting.

The twist imparted by the tube 42 runs back in the yarn 10 over the guide 20 to the bail (not shown) at the yarn exit end of the tube 40. The bail in the tube 40 acts as a twist stopper for the twist in the yarn running back from the tube 42.

In practice, we have found it desirable, in order to insure that the bail in tube 40 does effectively act as a twist stopper, to wrap the yarn twice around this bail, while we have found it sufficient to wrap the yarn only once around the bail of the tube 42.

After passing through twist tube 42, the yarn passes over a guide 22 and over a further guide 23. The yarn is passed a number of times (only one shown) around a rubber surfaced roller 23, and between the nip of the roller 23 and a steel roller 24 pressed into engagement therewith. The roller 24 is mounted on a driving shaft 44 driven in a known manner by means of an electric motor through suitable gearing (not shown). The yarn is gripped by the rollers 23, 24 which are operable to draw the yarn from the supply package 11. The yarn then passes over a traverse guide 25 onto a take-up package 26.

It is to be observed that by means of the rollers 23 and 24, the yarn is drawn under tension through both of the false twist operations. Hence, the yarn during both the first and the second false twist operation, i.e., prior to passing through tube 40 and also when passing between tubes 40 and 42, is subjected to positive tension. Further, the tension in the yarn during the second false twist operation is higher than during the first false twist operation.

The traverse guide 25 is mounted on a wire traverse member 45 formingpart of a yarn traverse mechanism of the kind disclosed in British Pat. No. 885,473.

The package 26 is wound onto a bobbin 46 disposed on a mandrel 47. The mandrel is in turn arranged to be rotatably mounted in the framework (not shown for the sake of clarity) so that the package 26 rests on and is driven by a cork covered roll 27. The roll 27 is mounted on a shaft 48 which is driven by an electric motor via gearing (not shown).

In operation, the false twist applied by the head 18 runs back in the yarn over the heater 17 as far as the tensioner 14, so that twisted yarn is subjected to heat setting as it passes over the heater 17. The equal and opposite false twist applied by head 21 runs back from the head 21 to the point at which it is detwisted in the tube 40, i.e., at the bail in tube 40. We believe that at this point the yarn after being twisted in one direction is detwisted and then immediately twisted in the opposite direction while still in a condition to be permanently deformable to some extent. As the yarn travels to the head 42 we believe it is further set in its oppositely twisted configuration, whereby a further crimping is superimposed on the crimping provided by the first false twisting and heating operation. I

To effect this further superimposed crimping on the first crimping we have found that the temperature of the heater 17, the length of yarn path between the exit end of the heater l7 and the tube 40, and the through-put speed of the yarn are all variable factors which should be arranged and correlated such that the yarn at the point of detwisting is in a condition to be still capable of at least some permanent deformation. However, we have surprisingly found that with each of these three which, compared to conventional single false twist crimped yarn, has greatly reduced or even zero torque, less stretch but good bulkiness, and which has no tendency to snarl.

The length of the yarn path between the twist tubes 40 and 42 can be adjusted by raising or lowering the yarn guide 20.

This adjustment allows the temperature 'or condition of the yarn entering the second twist tube 42 to be controlled.

The second embodiment of apparatus according to the invention, part of which is shown in FIG. 2, is in the main part the same as that illustrated in FIG. 1, but instead of using two separated twisting heads 18 and 21 (FIG. 1) to carry and rotate two twist tubes 40 and 42, a single false twist head 30 having two twist tubes 31 and 32 (as disclosed in greater detail in our US. Pat. No. 3,403,566 is provided. The tubes are driven by a pulley 33 driven in turn from belt 19 and are maintained in position by a magnet arrangement 34. A guide 35 is supported above the tubes 31 and 32 to guide the yarn from one tube 32 to the other. The guide 35 is mounted on a nonmagnetic bracket 36 secured to the magnet arrangement 34.

Referring to FIG. 3 of the drawings, which illustrates another apparatus for carrying out the methods herein described, after passing over the heating surface 17 the yarn passes through a false twisting apparatus indicated generally by the reference numeral 118, the apparatus being shown in greater detail in FIGS. 4 to 7. The parts of the apparatus not illustrated in FIGS. 3 to 7 are the same as in FIGS. 1 and 2.

The yarn after leaving the false twisting apparatus passes over a guide 119 and afurther guide 120. i

Referring now to FIG. 4 of the drawings, the false twisting apparatus 118 of FIG. 3 is shown to an enlarged scale in greater detail. The apparatus comprises a base plate 130 which is adjustably mounted on a supporting structure not shown. The upper face of the plate 130 is formed with a step indicated by the reference numeral 131 against which a lug 132 formed on one side of a vertically extending hollow cylindrical housing 133 abuts. The lug 132 is secured to the upper face of the plate 130 by a single large Allen screw 134 located in a stepped bore 135 formed in the lug 132, the underside of the head of the screw abutting the step in the bore to clamp the lug to the plate 130.

Located within the hollow cylindrical housing 133 is a self lubricating bush 136 supported in the housing by an inwardly extending spigot 137 fixed in the wall of the housing. A hollow cylindrical sleeve 138 is rotatably mounted in the bush 136 and is formed at its upper end with an annular flange 139 which overlies and engages with the upper end of the housing 133. Secured in the remote ends of the housing 138 are roller bearings 1411, 141 respectively which rotatably support a verticallyextending shaft 142 which extends into the housing from the lower end thereof. The lower end of the shaft located outside the housing 142 is drivably engaged by a belt 143 movably driven in known manner. The inner annulus of the bearing 140 abuts an upwardly facing shoulder 144 formed adjacent the upper end of the shaft and is secured thereto by an internally screw threaded sleeve 145 which is in screw threaded engagement with the upper end of the shaft. The inner annulus of the bearing 141 abuts a further shoulder 146 formed on the shaft and is secured thereto by an internally screw threaded collar 147 which engages the other side of the inner annulus and is in screw threaded engagement with a screw threaded part of the shaft.

A plate 148 having an opening 149 which encircles the upper end of the sleeve 138 is secured to the flange 139 on the sleeve by means of screws 150. The plate 148, the shape of which is best seen in FIGS. 5 and 6, extends to one side of the housing 133 and is formed with a further opening 151 in which is shrunk the upper end of an annular housing 152. The plate 148 is formed with a number of spaced projecting bosses 153 which support a cover plate 154 secured by a screw 155 to the boss 153 at the centre of the plate.

The annular housing 152 is formed around its inner periphery with an upwardly facing shoulder 156 against which the outer annulus of a roller bearing 157 abuts. The inner annulus of the bearing encircles and is secured to a generally cylindrical housing 158. The upper end of the cylindrical housing 158 is encircled by a ring 159, the outer periphery of which is drivably connected by a belt 160 to the sleeve 145 secured to the shaft 142. Rotation of the shaft 142 thereby effects rotation of the cylindrical housing 158. The upper end of the ring 159 projects through an opening 161 formed in the aforesaid plate 154 and located in a cup-shaped housing formed in the upper end of the ring is an annular member 162 formed in Prescallin the inner surface of which is hellmouthed as indicated by the reference numeral 163. A similar cup-shaped housing 164 is formed at the lower end of the cylindrical housing 158 in which a similar Prescallin annular member 165 is located.

integrally formed to one side of the: cylindrical housing 133 is a further hollow cylindrical housing 167. The inner surface of the housing 167 is formed with a step 168 against which abuts the outer race of a ball bearing 169. The inner annulus of the ball bearing supports a cylindrical housing 170 which is similar to the aforesaid housing 158. The housing 170 is encircled at its lower end by a ring 171 which is drivably connected by a belt 172 to the part of the shaft 142 below the shoulder 146 thereon. The housing 170 is thereby rotated by the shaft. The lower end of the ring 171 is formed with a cupshaped housing in which an annular member 173 formed in Prescallin is located. The inner surface of the annular member 173 is bell-mouthed as indicated by the reference numeral 174. The upper end of the cylindrical member 170 is formed with a cupshaped housing 175 in which a further Prescallin annular member 176 is located having a bell-mouthed inner surface indicated by the reference numeral 177. Formed on the lower side of the housing 133 and adjacent housing 167 are projecting bosses 178 against the lower faces of which a plate 179 abuts and is secured to the center boss by a screw 180. The plate is formed with openings 181 and 182 for the shaft 142 and lower end of the ring 171 respectively.

Secured to the upper face of the aforesaid plate 154 and in axial alignment with the shaft 142 is a spigot 183. The spigot is formed with a shoulder 184 against which abuts a roller bearing 185 on which a pulley wheel 186 is mounted. The roller bearing is secured the shoulder 184 by means of an internally screw threaded sleeve 187 secured to the upper end of the spigot 183.

As indicated earlier, the cylindrical sleeve 138 is rotatably mounted in the housing 133. Swinging movement of the plate 148 which is secured to the housing 133 is limited in one direction by engagement of the plate with an adjustable screw 188 mounted on the lug 132 as shown in FIG. 6 of the drawings. In this position, the aforesaid cylindrical housings 158 and 170 are out of axial alignment with one another. A tension spring 189 is secured at its end to upstanding posts 190 and 191 on the plate 130 and plate 148 respectively and acts to swing the plate into the position shown in FIG. 6. A locking mechanism for locking the plate in the position shown in FIG. 5 in which the cylindrical housings 158 and 159 are in axial alignment is shown in FIG. 7 and comprises a plunger 192 which is slidably mounted in a stepped bore 194 formed in a cylindrical boss 195 on the plate 148. The lower end of the plunger 192 is formed with a head 196 which is engageable with a laterally extending bracket 197 secured to one side of the housing 133 when the plate 148 is moved into a position in which the cylindrical housings 158, 1701 are in axial alignment. The plunger 192 is formed in the bore 194 with a collar 198 which abuts the step in the bore on one side thereof and is engaged on the other side thereof by one end of a compression spring 199 the other end of which acts against a ring 200 secured at the end of the bore 194 in the plate 148. Depression of the plunger 192 against the action of the spring 199 brings the head 196 of the plunger into engagement with the bracket 197 when, as indicated above, the plate 148 is in the position with the housings 158, 170 in axial alignment.

Release of the head 196 of the plunger from the bracket 197 allows the spring 189 to swing the plate 148 into the position shown in FIG. 6 in which, as indicated above, the cylindrical housings 158, 170 are out of axial alignment.

It is convenient in loading the false twisting apparatus with yarn to arrange the cylindrical housings 158, 170 in axial alignment. The yarn 10, after passing over the heater 17, is then fed through the housing 170, the housing 158, around the wheel 186 and back through the housing 58 and then to the ceramic guide 119. The plunger 192 is then released from the bracket 197 to allow the plate 148 to swing into the position shown in FIG. 6 so that the cylindrical housings 158, 170 are moved out of axial alignment. As shown in FIG. 3 of the drawings, the outlet end of the heating surface 17 is disposed to one side of the annular member 174 so that the yarn when tensioned by the rollers 121, 122 engages the curved surface 174 of the member 173. The yarn then passes over the curved surface 177 of the annular member 176 to the curved surface 166 of the annular member 165 and then over the curved surface 163 of the annular member 62 to the wheel 186. The surfaces 174, 177, 166 and 163 which the yarn engages roll the yarn to effect a first twisting of the yarn. Twist thus formed in the yarn runs back to the aforesaid yarn twist stopper 14 so that the twist in the part of the yarn adjacent the heating surface 17 is set in the yarn. The yarn after leaving the wheel 186 again passes without any further heating over the surface 163 of the member 62 and the surface 166 of the annular member 165 but this time in the opposite direction so that the yarn is twisted in the opposite direction. Residual heat left in the yarn from heating by the hater 16 causes the second twist to be set in the yarn.

It will be appreciated that the embodiment of the false twisting apparatus described above, the cylindrical housings 158, 159 are rotated at the same speed by the shaft 142.

The following examples are given to illustrate the invention and to provide comparison of crimped yarn produced by the invention with conventional single false twist crimped yarn.

EXAMPLE 1 A. Single end ISO-denier 30-f1lament polyester yarn was crimped by means of the apparatus illustrated in FIG. 1. The rotational speed of both twist tubes 40 and 42 was 260,000 r.p.m., and the yarn through-put speed was adjusted so that the yarn was twisted to 70 turns per inch by each twist tube. The tension in the yarn before the heater was arranged to be approximately 8 gms. The yarn path length between the heads 18 and 20-was approximately 12 inches, and the yarn path between the heater 17 and the false twist head 18 was approximately inches.

Yarn samples were produced at four different heater temperatures and the Dry Heat Retraction of each sample and'the spirality of fabric formed from each sample was measured with the following results:

Temperature Dry Heat Retrnction Spirality 235C 33% 4 2 direction 215C 28% 3 2 direction 195C 23% 2 2 direction 175C 16% 6 a direction B. The same procedure as in (A) was adopted except that the yarn after passing through the tube 40 of head 18' was guided, without passing through tube 42, directly'to the feed rollers 23, 24 then to the take-up package 26, so that the yarn was in fact subjected to a conventional single false twist crimping 8 ExAMriE 2 The same procedure was adopted as in Example 1 except that the rotational speed of tubes 40 and 42 was 200,000

rpm, and in this case the results were as follows for yarn crimped by means of the invention:

Temperature Dry Heat Retraction Spirality 235C 37% 3 Z direction 215C 33% 3 S direction 195C 30% 5' S direction 175C 28% 8 S direction In comparison, the results for conventional single false twist crimped yarn in this example were as follows:

The same procedure was adopted as in Example 1 except that 75-denier l6-filarnent polyester yarn was used, the rotational speed of tubes 40 and 42 was 325,000 r.p.m., the yarn through-put speed was adjusted so that the yarn was twisted to 80 turns per inch by each twist tube, and the tension in the yarn before the heater was arranged to be approximately 10 gms.

In this case the results were as follows for yarn crimped by means of the invention:

Temperature Dry Heat Retraction Spirality 235C 30.5% 1 2 215C 26.5% 4 S 195C 7 21% 7 S 175C 6% 9 5 In comparison the results for conventional single false twist crimped yarn in this example were as follows 1 Temperature Dry Heat Retraction Spirality 235C 52% 48 S 215C 47% 48 S 195C 47% 49 8 175C 39% 53 5 EXAMPLE 4 operation. In this case the results were as follows:

Temperature Dry Heat Retraction Spirality 235C 42% 19 S direction 215C 61% 20 S direction- 195C 58% 13 S direction 175C 52% 15 S direction The same procedure was adopted as in Example 1 except that 200-denier ZO-filament nylon yarn was used, the rotational speed of tubes 40 and 42 was 150,000 rpm, the yarn through-put speed was adjusted so that the yarn was twisted to' Temperature Pro-Relaxed Crimp Rigidity Spirality 235C 20.5% 0

215C 15% 1.5 2 195C 8% 4.0 2 F 8.5% 10.0 2

In comparison the results for conventional single false twist crimped yarn in this example were as follows: 7

Temperature Pro-Relaxed Crimp Rigidity Spirality 235C 7 30% 28 S 1 215C 21.5% 32S C 20.5% 35 5 175C 14.5% 40S In the above examples the Dry Heat Retraction was measured by. forming the yarn into a hank of 47 wraps, loading the hank with 14 grams, (to provide a load of 0.0001 gins/den.)

Dry Heat Retraction was the percentage decrease inle'ngthof the hank after heating.

The spirality was measuredTylmitting the yarn on a 300- needle circular machine into a tubular swatch, scouring and dyeing the swatch and then measuring the angle of the wale line to the longitudinal axis of the swatch, this angle being the spirality angle.

The pre-relaxed crimp rigidity was measured by relaxing a 300-meter length of yarn in bank form in water at 80 C. for 20 minutes, drying the hank in the atmosphere, forming the yarn into a new hank of 20 wraps, loading the hank under water with 400 gms., and then with 8 gms., the contraction in length upon reducing the loading to 8 gms. divided by the length under the 400 gm loading giving the crimprigidity.

It is to be noted that in these examples S direction spirality in the fabric is the spirality resulting from the effect of the first false twist operation, while Z direction spirality is the spirality resulting from the second false twist operation. Fabric of zero spirality, i.e., incorporating completely non-torque yarn, is produced when the spirality effects of the two false twist operations exactly cancel out. It is also to be noted that where yarn was crimped in accordance with the invention in the examples, substantially non-torque crimped yarn was produced.

What is claimed is:

l. A method of crimping yarn on the run including the steps of heating the yarn, subjecting the yarn to a first false twisting operation in one direction so that the yarn is heated in its first twisted configuration, and then subjecting the yarn to a second false twisting operation in the opposite direction without further heating, the yarn being oppositely twisted by the second false twisting operation while it still possesses suiticient heat to be at least partly permanently deformable.

2. A method as claimed in claim 1 wherein cooling of the yarn after said heating and before the first false twisting operation is impeded.

3. A method as claimed in claim 1 wherein the yarn is subjected during heating to a temperature of the order of 150 to 250 C.

4. A method as claimed in claim 1 wherein the twists imparted by the two false twisting operations are equal in magnitude.

5. Apparatus for crimping yarn comprising a first false twist device arranged to rotate the yarn in one direction, a heater so disposed as to heat the yarn as it travels to the first false twist device, a second false twist device arranged to rotate the yarn in the opposite direction, and guide means for guiding the yarn without further heating from the first false twist device to the second false twist device, each of the false twist devices com prising means defining an endless movable track provided with a surface for frictionally engaging the yarn, means for driving the track, and means for guiding the yarn into fn'ctional engagement with the surface in a direction such that the surface moves transversely to the direction of movement of the yarn.

6. Apparatus for crimping yarn, comprising means defining an endless movable track provided with a surface for frictionally engaging the yarn, means for driving the track, and means for guiding the yarn into frictional engagement with the surface in a first direction such that the surface moves transversely to the direction of movement of the yarn to twist the yarn in a predetermined sense and for then guiding the yarn into frictional engagement with the surface in a second direction such that the surface moves transversely to the direction of movement of the yarn to twist the yarn in the opposite sense.

7. An apparatus for crimping yarn comprising a false twist device consisting of an'endless movable track having a surface for frictionally engaging the yarn, means for advancing yarn under tension from a supply ofyai'n, guide means for guiding the yarn so that it crosses said surface substantially transversely to the direction of movement to the surface first in one direction whereby a first twist is imparted to the yarn in one direction and then in the opposite direction whereby a second twist is imparted to the yarn in the opposite direction, and a heater for heating the yarn passing in said one direction to the surface of the endless track.

8. A method of crrmpmg yarn on the run mcludmg the steps of false twisting the yarn a first time in one direction and heating the yarn while twisted, and then false twisting the yarn a second time in the opposite direction, the yarn being untwisted from the first false twisting operation and oppositely twisted by the second false twisting operation while it possesses sufiicient heat to be at least partly permanently deformable.

9. A method of crimping yarn on the run including the steps of heating the yarn, subjecting the yarn to a first false twisting operation in one direction so that the yarn is heated in its first twisted configuration, and then subjecting the yarn to a second false twisting operation in the opposite direction, the yarn being untwisted from the first false twisting operation and oppositely twisted by the second false twisting operation while it possess sufficient heat to be at least partly permanently deformable.

10. A method as claimed in claim 9 further including the step of impeding any cooling of the yarn before the first false twisting operation.

it 1. A method as claimed in claim 9 wherein the yarn is subjected during heating to a temperature of the order of 150 to 12. A method as claimed in claim 9 wherein the twists imparted by the two false twisting operations are equal in magnitude.

13. A method of crimping yarn on the run including the steps of heating and false twisting the yarn a first time in one direction so that the yarn is in a twisted configuration when being heated, and immediately false twisting the yarn a second time in the opposite direction so that the yarn is twisted in the opposite direction by the second false twisting simultaneously with being detwisted from the twist in said one direction imparted by the first false twisting, the yarn being oppositely twisted by the second false twisting operation while it still possesses sufficient heat to be at least partly permanently deformable.

14. A method according to claim 8, in which the yarn is comprised of a thermoplastic material.

l5. A method according to claim 14, in which said thermoplastic material is a polyester or a polyamide.

116. A method of crimping yarn on the run including the steps of false twisting the yarn a first time in one direction and heating the yarn 'while twisted, and then false twisting the yarn a second time in the opposite direction without heating the yarn between the first and second false twisting steps, the yarn being oppositely twisted by the second false twisting operation while it still possesses sufficient heat to be at least partly permanently deformable.

17. A method of crimping yarn on the run including the steps of heating the yarn, subjecting the yarn to a first false twisting operation in one direction so that the yarn is heated in its first twisted configuration, and then subjecting the yarn to a second false twisting operation in the opposite direction without further heating, the yarn being oppositely twisted by the second false twisting operation while it still possesses sufficient heat to be at least partly permanently deformable.

i it l 

1. A method of crimping yarn on the run including the steps of heating the yarn, subjecting the yarn to a first false twisting operation in one direction so that the yarn is heated in its first twisted coNfiguration, and then subjecting the yarn to a second false twisting operation in the opposite direction without further heating, the yarn being oppositely twisted by the second false twisting operation while it still possesses sufficient heat to be at least partly permanently deformable.
 2. A method as claimed in claim 1 wherein cooling of the yarn after said heating and before the first false twisting operation is impeded.
 3. A method as claimed in claim 1 wherein the yarn is subjected during heating to a temperature of the order of 150* to 250* C.
 4. A method as claimed in claim 1 wherein the twists imparted by the two false twisting operations are equal in magnitude.
 5. Apparatus for crimping yarn comprising a first false twist device arranged to rotate the yarn in one direction, a heater so disposed as to heat the yarn as it travels to the first false twist device, a second false twist device arranged to rotate the yarn in the opposite direction, and guide means for guiding the yarn without further heating from the first false twist device to the second false twist device, each of the false twist devices comprising means defining an endless movable track provided with a surface for frictionally engaging the yarn, means for driving the track, and means for guiding the yarn into frictional engagement with the surface in a direction such that the surface moves transversely to the direction of movement of the yarn.
 6. Apparatus for crimping yarn, comprising means defining an endless movable track provided with a surface for frictionally engaging the yarn, means for driving the track, and means for guiding the yarn into frictional engagement with the surface in a first direction such that the surface moves transversely to the direction of movement of the yarn to twist the yarn in a predetermined sense and for then guiding the yarn into frictional engagement with the surface in a second direction such that the surface moves transversely to the direction of movement of the yarn to twist the yarn in the opposite sense.
 7. An apparatus for crimping yarn comprising a false twist device consisting of an endless movable track having a surface for frictionally engaging the yarn, means for advancing yarn under tension from a supply of yarn, guide means for guiding the yarn so that it crosses said surface substantially transversely to the direction of movement to the surface first in one direction whereby a first twist is imparted to the yarn in one direction and then in the opposite direction whereby a second twist is imparted to the yarn in the opposite direction, and a heater for heating the yarn passing in said one direction to the surface of the endless track.
 8. A method of crimping yarn on the run including the steps of false twisting the yarn a first time in one direction and heating the yarn while twisted, and then false twisting the yarn a second time in the opposite direction, the yarn being untwisted from the first false twisting operation and oppositely twisted by the second false twisting operation while it possesses sufficient heat to be at least partly permanently deformable.
 9. A method of crimping yarn on the run including the steps of heating the yarn, subjecting the yarn to a first false twisting operation in one direction so that the yarn is heated in its first twisted configuration, and then subjecting the yarn to a second false twisting operation in the opposite direction, the yarn being untwisted from the first false twisting operation and oppositely twisted by the second false twisting operation while it possess sufficient heat to be at least partly permanently deformable.
 10. A method as claimed in claim 9 further including the step of impeding any cooling of the yarn before the first false twisting operation.
 11. A method as claimed in claim 9 wherein the yarn is subjected during heating to a temperature of the order of 150* to 250* C.
 12. A method as claimed in claim 9 whereIn the twists imparted by the two false twisting operations are equal in magnitude.
 13. A method of crimping yarn on the run including the steps of heating and false twisting the yarn a first time in one direction so that the yarn is in a twisted configuration when being heated, and immediately false twisting the yarn a second time in the opposite direction so that the yarn is twisted in the opposite direction by the second false twisting simultaneously with being detwisted from the twist in said one direction imparted by the first false twisting, the yarn being oppositely twisted by the second false twisting operation while it still possesses sufficient heat to be at least partly permanently deformable.
 14. A method according to claim 8, in which the yarn is comprised of a thermoplastic material.
 15. A method according to claim 14, in which said thermoplastic material is a polyester or a polyamide.
 16. A method of crimping yarn on the run including the steps of false twisting the yarn a first time in one direction and heating the yarn while twisted, and then false twisting the yarn a second time in the opposite direction without heating the yarn between the first and second false twisting steps, the yarn being oppositely twisted by the second false twisting operation while it still possesses sufficient heat to be at least partly permanently deformable.
 17. A method of crimping yarn on the run including the steps of heating the yarn, subjecting the yarn to a first false twisting operation in one direction so that the yarn is heated in its first twisted configuration, and then subjecting the yarn to a second false twisting operation in the opposite direction without further heating, the yarn being oppositely twisted by the second false twisting operation while it still possesses sufficient heat to be at least partly permanently deformable. 